1. Field of the Invention
The present invention relates to Ta and Ti precursors useful in the formation of a Ta-based or Ti-based material on a substrate, and includes tantalum amide precursors for formation of tantalum nitride on a substrate, and methods of use of such precursors for forming TaN material, e.g., thin film layers of TaN, on a substrate. The invention also contemplates single source compounds for the formation of TaSiN or TiSiN material on a substrate.
2. Description of the Related Art
Copper is of great interest for use in metallization of VLSI microelectronic devices because of its low resistivity, low contact resistance, and ability to enhance device performance (relative to aluminum metallization) via reduction of RC time delays thereby producing faster microelectronic devices. Copper CVD processes which are suitable for large-scale manufacturing and the conformal filling of high aspect ratio inter-level vias in high density integrated circuits are extremely valuable to the electronics industry, and are therefore being extensively investigated in the art.
Although CVD of Cu is gaining momentum in the semiconductor manufacturing industry, several problems still inhibit the integration of copper metallurgy in such microelectronic device applications. In specific, CVD of a suitable diffusion barrier for the copper metallization must be available to ensure the long-term reliability of the copper-based metallurgy in integrated circuits (ICs).
TaN and TaSiN have been demonstrated as a suitable metal diffusion barrier. A CVD process of TaN would obviously be advantageous and is currently the focus of development efforts by semiconductor equipment manufacturers. The CVD of TaN is at present carried out using Ta(NMe2)5, a solid source precursor, as the source reagent. However, Ta(NMe2)5 is a solid, and given the limited volatility of Ta(NMe2)5, new, robust and more volatile tantalum amide precursors are needed. The films deposited from such sources must be conducting, conformnal and of high purity. It would be extremely advantageous to utilize a suitable liquid source reagent as a tantalum amide precursor. For example, an alternative TaN precursor is Ta(NEt2)5, which is reportedly a liquid. However, this source reagent is unstable to elevated temperature conditions, readily decomposing to a tantalum imide species, Ta(NEt)(NEt2)3, upon heating, and thereby is an unsatisfactory candidate as a liquid source reagent for TaN barrier layer formation.
TaSiN and TiSiN are also currently being investigated in the art as diffusion barriers. A CVD process for these ternary barrier layer materials would also be advantageous and also is the focus of development efforts in the field. The CVD of TaSiN is at present carried out using Ta(NMe2)5 as the Ta source and silane as the silicon source. Further, TaCl5 in combination with silane and ammonia has been used to deposit TaSiN thin films. Apart from the hazards associated with handling a pyrophoric gas such as silane, the dual source reactor configuration required with such precursor species (TaCl5, Ta(NMe2)5 and silane) also increases the cost and complexity of the semiconductor manufacturing operation.
Another approach to barrier layer formation entails the PVD or CVD deposition of high purity Ta metal on the silicon substrate. The resulting Ta layer will form TaSix at the silicon contact region (i.e., the Ta bottom surface), and subsequent elevated temperature reaction of the Ta layer with a nitrogenous reactant such as NH3 or N2 will induce nitridation of the Ta top-surface. Thus, a TaSiN ternary diffusion barrier or a layered TaSi/TaN structure can be formed. This type of ternary diffusion barrier has been reported in the art and provides excellent contact resistance and diffusion barrier properties towards Cu metallization and integration of ferroelectric thin films.
In all instances of the formation of a Ta-based diffusion barrier, an effective CVD approach to conformally coat inter-level ( less than 0.15 xcexcm) vias and sidewalls is critical, and the CVD source reagent must be storage-stable, of appropriate volatility and vaporization characteristics, with good transport and deposition characteristics to produce a high-purity, electronic quality thin film.
There is a continuing and increasing need in the art for improved CVD source reagents for forming Ta-based diffusion barrier layers on microelectronic substrates, to facilitate copper metallization. Such CVD source reagents are desirably liquid in character, to facilitate their processibility using techniques such as liquid delivery CVD, wherein the liquid source reagent is rapidly vaporized, e.g., by flash vaporization on a heated element such as a grid, screen or porous metal body, to produce a volatilized source reagent. The resulting source reagent vapor can then be transported to the CVD chamber and contacted with a substrate maintained at appropriate elevated temperature, to effect the deposition on the substrate of the Ta-based material.
It therefore is an object of the present invention to provide useful precursor compositions for the formation of Ta-based material and Ti-based material on substrates.
It is another object of the invention to provide a method of forming a Ta-based material, such as TaN or TaSiN, or a Ti-based material, such as TiN or TiSiN, on a substrate, using such precursor compositions.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention relates generally to tantalum and titanium source reagents for the formation of Ta-based and Ti-based materials on a substrate by techniques such as chemical vapor deposition, and in particular and preferred practice of the invention, liquid delivery chemical vapor deposition.
As used herein, the term xe2x80x9cliquid deliveryxe2x80x9d when referred to chemical vapor deposition or other thin film or coating process refers to the fact that the precursor or source reagent composition for the material to be deposited on a substrate is vaporized from a liquid form to produce a corresponding precursor vapor which then is transported to the locus of deposition, to form the material film or coating on the substrate structure. The liquid phase which is vaporized to form the precursor vapor may comprise a liquid phase source reagent per se, or the source reagent may be dissolved in or mixed with a liquid to facilitate such vaporization to place the source reagent in the vapor phase for the deposition operation.
As used herein, the term xe2x80x9cperfluoroalkylxe2x80x9d is intended to be broadly construed to include groups containing alkyl moieties which are partially or fully substituted in fluorine atoms, and thus perfluoroalkyl includes for example a trifluoroalkyl substituent whose alkyl moiety is C1-C4 alkyl, such as trifluoromethyl.
In one compositional aspect, the present invention relates to a precursor composition comprising at least one tantalum and/or titanium species selected from the group consisting of:
(i) tethered amine tantalum complexes of the formula: 
wherein:
X is 2 or 3;
each of R1-R5 is independently selected from the group consisting of H, C1-C4 alkyl, aryl (e.g., phenyl), C1-C6 perfluoroalkyl (e.g., a trifluoroalkyl substituent whose alkyl moiety is C1-C4 alkyl, such as trifluoromethyl), and trimethylsilyl;
(ii) xcex2-diimines of the formula:
TaGxQ5xe2x88x92
wherein:
G is a xcex2-diimino ligand;
each Q is selected from the group consisting of H, C1-C6 alkyl, aryl and C1-C6 perfluoroalkyl; and
x is an integer from 1 to 4 inclusive;
(iii) tantalum diamide complexes of the formula
Ta(N(R1)(CH2)xN(R2))y(NR3R4)5xe2x88x922y
wherein:
x is 1 or2;
y is 1 or 2;
each of R1-R4xe2x80x94 is independently selected from the group consisting of H, C1-C4 alkyl, aryl, perfluoroalkyl, and trimethylsilyl;
(iv) tantalum amide compounds of the formula
Ta(NRRxe2x80x2)5
wherein each R and Rxe2x80x2 is independently selected from the group consisting of H, C1-C4 alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that in each NRRxe2x80x2 group, R Rxe2x80x2;
(v) xcex2-ketoimines of the formula 
wherein each of R1, R2, Ra, Rb, Rc and Rd is independently selected from H, aryl, C1-C6 alkyl, and C1-C6 perfluoroalkyl; and
(v) tantalum cyclopentadienyl compounds of the formula: 
wherein each R is independently selected from the group consisting of H, methyl, ethyl, isopropyl, t-butyl, trimethylsilyl;
(vii) Ta(NR1R2)x(NR3R4)5xe2x88x92x/Ti(NR1R2)x(NR3R4)4xe2x88x92x or Ta(NR1)(NR2R3)3 
where each of R1, R2, R3 and R4 are independently selected from the group consisting of H, C1-C8 alkyl (e.g., Me, Et, tBu, iPr, etc.), aryl (e.g., phenyl), C1-C8 perfluoroalkyl (e.g., CF3 or a fluoroalkyl whose alkyl moiety is C1-C4, such as trifluoromethyl), or a silicon-containing group such as silane (SiH3), alkylsilane, (e.g., SiMe3, Si(Et)3, Si(iPr)3, Si(iPr)3, Si(tBu)3, perfluoroalkylsilyl (e.g., Si(CF3)3), triarylsilane (e.g., Si(Ph)3), or alkylsilylsilane (e.g., Si(SiMe3)x(Me)3xe2x88x92x);
(viii) Ta(SiR1R2R3)x(NR4R5)5xe2x88x92x/Ti(SiR1R2R3)x(NR4R5)4xe2x88x92x 
where R1-5 can any be combination of H, Me, Et, tBu, Ph, iPr, CF3, SiH3, SiMe3, Si(CF3)3, Si(Et)3, Si(iPr)3, Si(tBu)3, Si(Ph)3, Si(SiMe3)x(Me)3xe2x88x92x and Si(SiMe3)x(Me)3xe2x88x92x; and
(ix) (Cpn)Ta(SiR1R2R3)x(Cpn)2Ti(SiR1R2R3)(NR4R5)
where R1-5 can any be combination of H, Me, Et, tBu, Ph, iPr, CF3, SiH3, SiMe3, Si(CF3)3, Si(Et)3, Si(iPr)3, Si(tBu)3, Si(Ph)3, Si(SiMe3)x(Me)3xe2x88x92x and Cpn is C5HxMe(5xe2x88x92x) (where x=0-5).
In one aspect, the present invention relates to tantalum amide precursors for formation of tantalum nitride on a substrate, and to methods of forming TaN material on a substrate from such precursors, wherein the precursor composition comprises at least one tantalum species selected from the group consisting of:
(i) tethered amine tantalum complexes of the formula: 
wherein:
X is 2 or 3;
each of R1-R5 is independently selected from the group consisting of H, C1-C4 alkyl, aryl (e.g., phenyl), C1-C6 perfluoroalkyl (e.g., a trifluoroalkyl substituent whose alkyl moiety is C1-C4 alkyl, such as trifluoromethyl), and trimethylsilyl;
(ii) xcex2-diimines of the formula:
TaGxQ5xe2x88x92x
wherein:
G is a xcex2-diimino ligand;
each Q is selected from the group consisting of H, C1-C6 alkyl, aryl and C1-C6 perfluoroalkyl; and
x is an integer from 1 to 4 inclusive;
(iii) tantalum diamide complexes of the formula
Ta(N(R1)(CH2)xN(R2))y(NR3R4)5xe2x88x922y
wherein:
x is 1 or 2;
y is 1 or 2;
each of R1-R4xe2x80x94 is independently selected from the group consisting of H, C1-C4 alkyl, aryl, perfluoroalkyl, and trimethylsilyl;
(iv) tantalum amide compounds of the formula
Ta(NRRxe2x80x2)5
wherein each R and Rxe2x80x2 is independently selected from the group consisting of H, C1-C4 alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that in each NRRxe2x80x2 group, R Rxe2x80x2;
(v) xcex2-ketoimines of the formula 
wherein each of R1, R2, Ra, Rb, Rcand Rd is independently selected from H, aryl, C1-C6 alkyl, and C1-C6 perfluoroalkyl; and
(vi) tantalum cyclopentadienyl compounds of the formula 
wherein each R is independently selected from the group consisting of H, methyl, ethyl, isopropyl, t-butyl, trimethylsilyl.
In another aspect, the present invention relates to a tantalum amide precursor composition for forming a tantalum nitride material on a substrate, including at least one tantalum amide species selected from the above-described selection group, and a solvent for such tantalum amide species. The solvent may be selected from the group consisting of C6-C10 alkanes, C6-C10 aromatics, and compatible mixtures thereof. Illustrative alkane species include hexane, heptane, octane, nonane and decane. Preferred alkane solvent species include C8 and C10 alkanes. Preferred aromatic solvent species include toluene and xylene. In the most preferred approach, no solvent is required to deliver the liquid source reagents.
In another aspect, the invention relates to a method of forming a tantalum nitride material on a substrate from a precursor composition therefor, including the steps of vaporizing the precursor composition to form a precursor vapor and contacting the precursor vapor with a substrate under deposition conditions to deposit on the substrate the tantalum nitride material, wherein the tantalum nitride precursor composition comprises at least one tantalum amide species selected from the above-described selection group of tantalum compounds and complexes, in a solvent for the tantalum amide species.
The tantalum nitride precursor composition thus may be provided as a liquid composition, which is delivered to a vaporizer to effect vaporization and formation of the tantalum nitride precursor vapor, with the vapor being transported to a deposition zone containing the substrate for the formation of the tantalum nitride material on the substrate. The formation of tantalum nitride material on the substrate may be carried out by a deposition process such as chemical vapor deposition, assisted chemical vapor deposition, ion implantation, molecular beam epitaxy and rapid thermal processing.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.